Modern integrated circuits (ICs) are formed on semiconductor chips (also referred to as dies). To increase manufacturing throughput and lower manufacturing costs, the ICs are manufactured in semiconductor wafers, each containing many identical semiconductor chips. After the ICs are manufactured, semiconductor chips are sawed from the wafers and packaged before they can be used.
In typical packaging processes, semiconductor chips are first attached to package substrates. This includes physically securing the semiconductor chips on the package substrates and connecting bonding bumps on the semiconductor chips to bonding bumps on the package substrates. Underfill, which typically comprises epoxy, is used to further secure the bonding. The semiconductor chips may be bonded using either flip-chip bonding or wire bonding. The resulting packages are referred to as ball grid array (BGA) modules. A plurality of chips having different functions may be integrated in a same BGA module to form a system-in-package (SIP) module.
Flip-chip bonding utilizes conductive bumps to establish electrical contact between a chip's contact pads and the package substrate. The bumps themselves, based on the material used, are classified as solder bumps, gold bumps, copper pillar bumps and bumps with mixed metals. However, there are challenges to implementing such features and processes in ICs fabrication. For example, it is difficult to achieve accurately bump alignment of the chip to the package substrate (both having bumps) if the bumps have been reflowed, thereby increasing the likelihood of an open circuit.